Monday, May 20, 2013

1305.4108 (A. D. Christianson et al.)

Doping dependence of the the spin excitations in Fe-based
superconductors Fe1+yTe1-xSex

A. D. Christianson, M. D. Lumsden, K. Marty, C. H. Wang, S. Calder, D. L. Abernathy, M. B. Stone, H. A. Mook, M. A. McGuire, A. S. Sefat, B. C. Sales, D. Mandrus, E. A. Goremychkin
The Fe1+yTe1-xSex series of materials is one of the prototype families of Fe-based superconductors. To provide further insight into these materials we present systematic inelastic neutron scattering measurements of the low energy spin excitations for x=0.27, 0.36, 0.40, 0.49. These measurements show an evolution of incommensurate spin excitations towards the (1/2 1/2 0) wave vector with doping. Concentrations (x=0.40 and 0.49) which exhibit the most robust superconducting properties have spin excitations closest to (1/2 1/2 0) and also exhibit a strong spin resonance in the spin excitation spectrum below Tc. The resonance signal appears to be closer to (1/2 1/2 0) than the underlying spin excitations. We discuss the possible relationship between superconductivity and spin excitations at the (1/2 1/2 0) wave vector and the role that interstitial Fe may play.
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